1. Field of the Invention.
The present invention relates to systems for supplying conditioned air through a duct to a room. In particular, the present invention is a variable volume air conditioning system including means permitting service personnel to monitor actual air flow through the duct at the thermostat within the room.
2. Description of the Prior Art.
Variable volume air conditioning systems heat and cool rooms by adjusting the rate of flow (i.e. velocity) of air into each room or zone. The temperature of the incoming air remains constant. Air conditioning systems of these and other types, as well as apparatus for use therein, are disclosed in the following U.S. patents.
Travaglio et al. U.S. Pat. No. 3,941,310 PA1 McNabney U.S. Pat. No. 3,719,321 PA1 Ginn et al. U.S. Pat. No. 4,077,567 PA1 Leemhuis U.S. Pat. No. 4,147,298 PA1 Bramow et al. U.S. Pat. No. 4,263,931 PA1 Bentsen U.S. Pat. No. 4,428,529 PA1 Maxson et al. U.S. Pat. No. 4,264,035 PA1 Bowman U.S. Pat. No. 4,422,571 PA1 Bowman U.S. Pat. No. 4,413,514 PA1 Kreuter U.S. Pat. No. 4,467,956
The above patents disclose pneumatic air conditioning systems in which a pneumatic signal representative of a desired air flow is coupled from a thermostat located in the room in which the temperature is being regulated, to the air flow regulating apparatus. The pneumatic signal is determined as a function of sensed or actual temperature within the room, and a desired temperature set by its occupants or other personnel.
Electrical systems for controlling air flow in variable volume air conditioning systems are also known. In one such system an electrical signal representative of desired air flow is coupled from the room thermostat to the air flow regulating apparatus. This signal is applied across an input port of a bridge-type hot-wire anomometer air velocity sensor mounted within the duct. Air flow through the duct is impinged upon one or more temperature-sensitive resistors of the bridge. A comparator coupled to an output port of the bridge senses its balance state and provides signals which are used to control motors which open and close a damper to regulate the flow of air through the duct.
The control circuitry and damper actuating mechanisms of the above-described air conditioning systems, whether they be pneumatic or electrically actuated, are typically located in the ceiling of the room, adjacent the duct. It is often necessary to determine whether the regulating apparatus is providing the proper flow of air in response to the signals from the thermostat when servicing these systems. To do so a technician must climb into the ceiling in order to take measurements or otherwise determine from the control circuitry the actual flow of air through the duct. These service procedures are not only inconvenient, but they disturb personnel working within the room as well.
It is evident that there is a continuing need for improved air conditioning systems. An air conditioning system which permits a service technician to quickly and easily monitor its performance would be especially desirable.